Methods for manufacturing bi-metallic catalysts having a controlled crystal face exposure

Abstract

Improved bi-metallic nanocatalysts are manufactured using a control agent to produce nanoparticles having a controlled crystal face exposure. The bi-metallic nanocatalyst particles are manufactured in a two-step process. In a first step, nanocatalyst particles are manufactured using the control agent and the primary metal atoms. The primary metal atoms and the control agent are reacted to form complexed metal atoms. The complexed metal atoms are then allowed or caused to form nanoparticles. The nanoparticles formed in the first step using the control agent have a desired crystal face exposure. In a second step, the secondary metal atoms are deposited on the surface of the primary metal nanoparticles. The secondary catalyst atoms maintain the same crystal face exposure as the primary metal nanoparticles.

1. A method for manufacturing a supported bi-metallic nanocatalyst having a controlled crystal face exposure, comprising,
 (i) preparing a solution comprised of a plurality of primary metal atoms composed of a first element and a plurality of control agent molecules and allowing the primary metal atoms and control agent molecules to react to form a complex; 
 (ii) allowing or causing the complexed metal atoms to form a plurality of first nanoparticles composed of the primary metal atoms having a controlled crystal face exposure; 
 (iii) thereafter depositing a plurality of secondary catalyst atoms composed of a second element that differs from the first element of the primary metal atoms on an outer surface of the first nanoparticles so as to form bimetallic nanoparticles composed of the first nanoparticles and the secondary catalyst atoms disposed on the outer surface of the first nanoparticles, the bimetallic nanoparticles having the same controlled crystal face exposure as the first nanoparticles; and 
 (iv) supporting the nanoparticles on a support material. 
 
     
     
       2. A method as in  claim 1 , in which the first nanoparticles have a (110) type crystal face exposure. 
     
     
       3. A method as in  claim 1 , in which the first nanoparticles have a (111) type crystal face exposure. 
     
     
       4. A method as in  claim 1 , in which (ii) comprises reducing the nanoparticles using a reducing agent. 
     
     
       5. A method as in  claim 4 , in which the reducing agent comprises hydrogen. 
     
     
       6. A method as in  claim 4 , wherein (ii) further comprises removing or oxidizing at least a portion of any free reducing agent remaining in the solution following reduction of the metal atoms. 
     
     
       7. A method as in  claim 1 , in which the primary metal atoms comprise a transition metal and the secondary metal atoms comprise a transition metal that is different from the primary metal atoms by at least one element. 
     
     
       8. A method as in  claim 1 , in which the control agent molecules comprise small organic molecules or highly branched oligomers or polymers. 
     
     
       9. A method as in  claim 1 , in which the control agent molecules comprise straight chain oligomers or polymers. 
     
     
       10. A method as in  claim 1 , in which the organic control agent molecules bond to the primary catalyst atoms though at least one functional group selected from the group consisting of a hydroxyl, a carboxyl, a carbonyl, an amine, an amide, a nitrile, a nitrogen with a free lone pair of electrons, an amino acid, a thiol, a sulfonic acid, a sulfonyl halide, and an acyl halide. 
     
     
       11. A method as in  claim 1 , in which the secondary catalyst atoms is deposited on the nanoparticles in solution so as to form bi-metallic colloidal nanoparticles. 
     
     
       12. A method as in  claim 1 , in which the secondary catalyst atoms are epitaxially grown on the surface of the nanoparticles so as to maintain the controlled crystal face exposure. 
     
     
       13. A method as in  claim 1 , in which at least a portion of the control agent molecules bond to the nanoparticles and to the support surface so as to tether the nanoparticles to the support material. 
     
     
       14. A method as in  claim 1 , wherein the metal loading of the catalyst nanoparticles on the support material is greater than about 0.1 wt %. 
     
     
       15. A method as in  claim 1 , where (iv) is performed before (iii). 
     
     
       16. A supported bi-metallic catalyst manufactured according to the method of  claim 1 . 
     
     
       17. A method of manufacturing hydrogen peroxide, comprising:
 placing the supported bi-metallic catalyst of  claim 16  in a reactor; and 
 introducing a hydrogen feedstream and an oxygen feedstream into the reactor under conditions suitable for catalyzing the production of hydrogen peroxide using the supported catalyst. 
 
     
     
       18. A method for manufacturing a supported bi-metallic nanocatalyst having a controlled crystal face exposure, comprising:
 (i) preparing a solution comprised of a plurality of primary catalyst atoms composed of a first element and a plurality of organic control agent molecules and allowing the primary catalyst atoms and control agent molecules to react to form a complex; 
 (ii) causing formation of colloidal nanoparticles having a controlled crystal face exposition by reducing the complex in the solution with a reducing agent; 
 (iii) removing or neutralizing at least a portion of any free reducing agent remaining in the solution following step (ii); 
 (iv) depositing, without the use of a control agent, a plurality of secondary catalyst atoms composed of a second element that differs from the first element of the primary catalyst atoms on an outer surface of the colloidal nanoparticles to form a plurality of bi-metallic colloidal nanoparticles; and 
 (v) supporting the bi-metallic nanoparticles on a support material. 
 
     
     
       19. A method as in  claim 18 , in which the primary catalyst atoms are a platinum group metal and the secondary metal atoms comprise a platinum group metal that is different from the primary metal atoms. 
     
     
       20. A method as in  claim 19 , in which the ratio of primary metal atoms to secondary metal atoms is in a range from about 1:1 to about 1000:1. 
     
     
       21. A method as in  claim 18 , in which the organic control agent molecules bond to the primary catalyst atoms though at least one functional group selected the group consisting of a hydroxyl, a carboxyl, a carbonyl, an amine, an amide, a nitrile, a nitrogen with a free lone pair of electrons, amino acid, a thiol, a sulfonic acid, a sulfonyl halide, and an acyl halide. 
     
     
       22. A method as in  claim 18 , in which the reducing agent is hydrogen. 
     
     
       23. A supported catalyst manufactured according to the method of  claim 18 . 
     
     
       24. A method of manufacturing hydrogen peroxide, comprising:
 placing the supported catalyst of  claim 23  in a reactor; and 
 introducing a hydrogen feedstream and an oxygen feedstream into the reactor under conditions suitable for catalyzing the production of hydrogen peroxide using the supported catalyst.